1. Field of the Invention
The present invention relates to a scanning microscope and particularly relates to a scanning microscope that has a spectroscopic detection function.
2. Description of the Related Art
In recent years, confocal scanning microscopes provided with a spectroscopic detection function have been developed and used. Such a microscope is disclosed in, for example, Japanese Laid-open Patent Publication No. 2006-010944.
Many confocal scanning microscopes provided with a spectroscopic detection function are used for fluorescence observations; however, as a general rule, fluorescence is weak so that the light quantity of the fluorescence obtained per unit time is small. Since a sample observed under a confocal scanning microscope is scanned at a high speed, only a short period of time is spent on exciting each point on the sample. Therefore, in order to obtain a bright image, it is necessary to efficiently lead a limited amount of generated fluorescence to a photodetector.
As disclosed in Japanese Laid-open Patent Publication No. 2006-010944, however, since currently used confocal scanning microscopes provided with a spectroscopic detection function use a reflective diffraction grating as spectroscopic means, high diffraction efficiency cannot be achieved for a wide wavelength region. This is because a reflective diffraction grating is generally a surface-relief diffraction grating which has the relief structure on the surface so as to obtain diffracted light and the diffraction efficiency of the surface-relief diffraction grating is on the order of 70% at most.
Spectroscopic means is generally an optical element that loses a large quantity of light; accordingly, in a confocal scanning microscope provided with a spectroscopic detection function, suppressing the light loss caused at spectroscopic means is effective to improve light-use efficiency.
A technology for suppressing light loss caused at spectroscopic means is disclosed in, for example, Japanese Laid-open Patent Publication No. 2006-153587. In Japanese Laid-open Patent Publication No. 2006-153587, by focusing attention on the characteristic depending on polarization direction of a reflective diffraction grating that is spectroscopic means, a technology is disclosed in which incident light is converted into S polarized light indicating higher diffraction efficiency so as to suppress light loss caused at the spectroscopic means.
Use of the technology disclosed in Japanese Laid-open Patent Publication No. 2006-153587 can improve the light-use efficiency of a confocal scanning microscope provided with a spectroscopic detection function.